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a45a2b86a0
Improves the tap tempo algorithm and usage, as well refactoring the code for better maintainability. --------- Co-authored-by: Dalton Messmer <messmer.dalton@gmail.com>
130 lines
3.3 KiB
C++
130 lines
3.3 KiB
C++
/*
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* TapTempo.cpp - Plugin to count beats per minute
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*
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* Copyright (c) 2026 saker <sakertooth@gmail.com>
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*
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* This file is part of LMMS - https://lmms.io
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public
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* License along with this program (see COPYING); if not, write to the
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* Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
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* Boston, MA 02110-1301 USA.
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*
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*/
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#include "TapTempo.h"
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#include <string>
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#include "SamplePlayHandle.h"
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#include "Song.h"
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#include "embed.h"
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#include "plugin_export.h"
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namespace lmms {
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extern "C" {
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Plugin::Descriptor PLUGIN_EXPORT taptempo_plugin_descriptor
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= {LMMS_STRINGIFY(PLUGIN_NAME), "Tap Tempo", QT_TRANSLATE_NOOP("PluginBrowser", "Tap to the beat"),
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"saker <sakertooth@gmail.com>", 0x0100, Plugin::Type::Tool, new PluginPixmapLoader("logo"), nullptr, nullptr};
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PLUGIN_EXPORT Plugin* lmms_plugin_main(Model*, void*)
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{
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return new TapTempo;
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}
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}
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TapTempo::TapTempo()
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: ToolPlugin(&taptempo_plugin_descriptor, nullptr)
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{
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m_intervals.fill(std::chrono::milliseconds::zero());
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}
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void TapTempo::tap(bool play)
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{
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using namespace std::literals;
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if (play)
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{
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const auto metronomeFile = m_beat == 0 ? "misc/metronome02.ogg" : "misc/metronome01.ogg";
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Engine::audioEngine()->addPlayHandle(new SamplePlayHandle(metronomeFile));
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}
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m_beat = (m_beat + 1) % Engine::getSong()->getTimeSigModel().getNumerator();
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if (m_lastTap.time_since_epoch() == 0ms)
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{
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m_lastTap = clock::now();
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return;
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}
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const auto delta = std::chrono::duration_cast<std::chrono::milliseconds>(clock::now() - m_lastTap);
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constexpr auto resetTime = 2000ms;
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if (delta >= resetTime)
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{
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m_bpm = 0;
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m_taps = 0;
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m_beat = 0;
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m_lastTap = clock::now();
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return;
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}
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m_intervals[(m_taps++) % MaxIntervals] = delta;
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constexpr auto millisecondsPerMinute = 60000.0;
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if (m_taps >= MaxIntervals)
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{
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// calculate the median of the stored intervals to reject outliers
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std::nth_element(m_intervals.begin(), m_intervals.begin() + m_intervals.size() / 2, m_intervals.end());
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const auto newBpm = millisecondsPerMinute / m_intervals[m_intervals.size() / 2].count();
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// use an adaptive EMA to smooth out jitter when in the ballpark and update quickly when moving to a new BPM
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const auto error = std::abs(newBpm - m_bpm);
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const auto alpha = std::clamp(error / 100.0, 0.2, 0.8);
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m_bpm = alpha * newBpm + (1.0 - alpha) * m_bpm;
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}
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else
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{
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// calculate the instant BPM for now until we have enough taps
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m_bpm = millisecondsPerMinute / delta.count();
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}
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m_lastTap = clock::now();
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}
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void TapTempo::sync()
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{
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Engine::getSong()->setTempo(std::round(m_bpm));
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}
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void TapTempo::reset()
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{
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m_bpm = 0;
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m_taps = 0;
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m_beat = 0;
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m_lastTap = std::chrono::time_point<clock>{};
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}
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QString TapTempo::nodeName() const
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{
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return taptempo_plugin_descriptor.name;
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}
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double TapTempo::bpm() const
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{
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return m_bpm;
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}
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} // namespace lmms
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